1. Field of the Invention
The present invention relates to a lens cover drive mechanism and, more particularly, to a lens cover drive mechanism for driving a lens cover of a camera.
2. Description of the Related Art
Cameras are known having a lens cover which is directly coupled to a lens cover drive mechanism, such that the lens cover drive mechanism opens and closes the lens cover. This type of conventional camera has an electric motor, a gear train, and a lens cover to cover an end of a lens barrel. The electric motor causes generation of a drive force, and the gear train transmits the drive force of the electric motor to the lens cover. The lens cover is integrally fixed to one of the gears of the gear train and integrally moves in a rotary motion accompanying the movement of the connected gear. Namely, the lens cover opens and closes at the front surface portion of the lens barrel by accompanying the rotary motion of the connected gear.
In the above-mentioned conventional camera, when an external force presses the lens cover, it is possible for breakage of a portion of the gear train or of the lens cover to occur. This is due to the fact that the lens cover and one of the gears which drive the lens cover are integrally fixed to each other. In a case that the lens cover becomes caught for some reason, the drive force to drive the lens cover places a strain on some portions of the lens cover drive mechanism and the lens cover, creating a risk of deformation or breakage of the portion on which the drive force has acted.
FIG. 7 shows another type of conventional camera having a lens cover and a lens cover drive mechanism. The shaft 1 has a protuberance 1 a which receives a drive force and rotates in the direction of arrow (a). The shaft 1 is fixed to an extension 2a of a member 2. The member 2 has a shaft portion 2b which is arranged in parallel to the shaft 1 and fits through a hole 3a of a transmission arm 3. The shaft portion 2b is slidable in the hole 3a. A coil spring 4 is fitted on the shaft 1 and urges the shaft portion 2b towards one side surface of the hole 3a. Through the coil spring 4, the contact state of the shaft portion 2b and the hole 3a is maintained. When the member 2 rotates, the shaft portion 2b does not slide in the hole 3a due to the urging force of the coil spring 4. Consequently, when the shaft portion 2b rotates, the transmission arm 3 is driven in the direction of arrow (b). The transmission arm 3 has a protuberance 3b at an opposite end from the hole 3a, and the protuberance 3b and a fulcrum 5a of a barrier (lens cover) 5 cooperate with each other. The barrier 5 is rotatable about the fulcrum 5a. When the transmission arm 3 is driven in the direction of the arrow (b), the barrier 5 rotates about the fulcrum 5a, and the barrier 5 is opened and closed.
When the barrier 5 is fixed in place by an external force, the transmission arm 3 does not move in the direction of arrow (b). In the fixed state of the barrier 5, when a drive force acts on protuberance 1 a, the coil spring 4 cannot maintain the shaft portion 2b in the same contact position in the hole 3a. The barrier 5 remains in place without the drive force being applied thereto. Thus, it becomes possible to allow the lens cover drive force to dissipate without damaging either the barrier (lens cover) or the lens cover drive mechanism.